Slotted antenna waveguide plasma source

Abstract

A high density plasma generated by microwave injection using a windowless electrodeless rectangular slotted antenna waveguide plasma source has been demonstrated. Plasma probe measurements indicate that the source could be applicable for low power ion thruster applications, ion implantation, and related applications. This slotted antenna plasma source invention operates on the principle of electron cyclotron resonance (ECR). It employs no window and it is completely electrodeless and therefore its operation lifetime is long, being limited only by either the microwave generator itself or charged particle extraction grids if used. The high density plasma source can also be used to extract an electron beam that can be used as a plasma cathode neutralizer for ion source beam neutralization applications.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0001]The invention described herein was made by an employee of the United States Government and may be manufactured and used by or for the Government for Government purposes without the payment of any royalties thereon or therefore.FIELD OF THE INVENTION[0002]The present invention relates to a plasma producing microwave antennas used for producing plasmas for use in ion thrusters, ion etching of surfaces, the embedding of ions within surfaces, production of electrons, and the like.BACKGROUND OF THE INVENTION[0003]Plasmas consist of gaseous complexes in which atoms or molecules are dissociated into free electrons, ions, free radicals, and neutral particles; stars, for instance, consist predominantly of plasmas. On earth, plasma occurs naturally in lightning bolts, flames, and similar phenomena, or may be manufactured by heating a gas to high temperatures, or by applying a strong electric field to a gas. Plasmas are calle...

AI Technical Summary

Benefits of technology

[0019]Yet another aspect of the present invention is to provide a plasma source that does not require a microwave window.

[0020]And a final asp

Problems solved by technology

Drawbacks of existing direct current (DC) ion sources include erosion, short service life of plasma generators, and plasma non-uniformity.

This is an undesirable attribute from the standpoint of materials processing, as contamination of the work product can result.

DC ion sources (and DC electron sources) have limited lifetimes due to being constantly subjected to erosion, and the cathodes that drive such plasma sources typically, over time, lose their ability to emit electrons so that eventually the cathodes fail.

This arrangement gives rise to peaked, non-uniform plasma density profiles at the exit plane.

Such non-uniform profiles give rise to non-uniform wear of the ion extraction grids—thereby leading to failure by structural degradation or by electron backstreaming.

The insulating window, typically boron nitride makes such devices impractical for ion sources or ion thruster applications because the insulating window will acquire a coating over time due to wear of the extraction grids.

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